tools: limit bgp route-maps to direct changes only

When using frr-reload.py to modify a bgp neighbors route-map
the code was doing this:

a) deleting the previous route-map: `no neighbor XX route-map YY (in|out)`
b) Adding the new route-map back in `neighbor XX route-may ZZ (in|out)`

Now imagine that we have an outgoing route-map that we are changing
and the reload is large because of a large number of lines in frr.conf

Item (a) will happen.  BGP will immediately start sending all local
routes.  At some point in time in the future (b) will be applied.
This of course causes a withdraw but for a short amount of time we
are leaking unintended routes.  This is bad for several reasons
not 1) route churn upstream, 2) we might influence traffic to go the
wrong way. 3) if upstream has a maximum-prefix command the routes
being sent might trip its circuitry and shutdown the peer entirely
not even allowing you to get to (b).

Ticket: #2589685
Signed-off-by: Donald Sharp <sharpd@nvidia.com>

diff --git a/tools/frr-reload.py b/tools/frr-reload.py
index 7cb8a2e7294efc200fd38ba84d7a6e70b6fb9265..eb8753fd088b36f732b520e6f96263bcc3018b32 100755 (executable)
--- a/tools/frr-reload.py
+++ b/tools/frr-reload.py
@@ -1390,6 +1390,53 @@ def ignore_delete_re_add_lines(lines_to_add, lines_to_del):
                                 if found_add_bfd_nbr:
                                     lines_to_del_to_del.append((ctx_keys, line))
 
+                """
+                Neighbor changes of route-maps need to be accounted for in that we
+                do not want to do a `no route-map...` `route-map ....` when changing
+                a route-map.  This is bad mojo as that we will send/receive
+                data we don't want.
+                Additionally we need to ensure that if we have different afi/safi
+                variants that they actually match and if we are going from a very
+                old style command such that the neighbor command is under the
+                `router bgp ..` node that we need to handle that appropriately
+                """
+                re_nbr_rm = re.search("neighbor(.*)route-map(.*)(in|out)$", line)
+                if re_nbr_rm:
+                    adjust_for_bgp_node = 0
+                    neighbor_name = re_nbr_rm.group(1)
+                    rm_name_del = re_nbr_rm.group(2)
+                    dir = re_nbr_rm.group(3)
+                    search = "neighbor%sroute-map(.*)%s" % (neighbor_name, dir)
+                    save_line = "EMPTY"
+                    for (ctx_keys_al, add_line) in lines_to_add:
+                        if ctx_keys_al[0].startswith("router bgp"):
+                            if add_line:
+                                rm_match = re.search(search, add_line)
+                            if rm_match:
+                                rm_name_add = rm_match.group(1)
+                                if rm_name_add == rm_name_del:
+                                    continue
+                                if len(ctx_keys_al) == 1:
+                                    save_line = line
+                                    adjust_for_bgp_node = 1
+                                else:
+                                    if (
+                                        len(ctx_keys) > 1
+                                        and len(ctx_keys_al) > 1
+                                        and ctx_keys[1] == ctx_keys_al[1]
+                                    ):
+                                        lines_to_del_to_del.append((ctx_keys_al, line))
+
+                    if adjust_for_bgp_node == 1:
+                        for (ctx_keys_dl, dl_line) in lines_to_del:
+                            if (
+                                ctx_keys_dl[0].startswith("router bgp")
+                                and len(ctx_keys_dl) > 1
+                                and ctx_keys_dl[1] == "address-family ipv4 unicast"
+                            ):
+                                if save_line == dl_line:
+                                    lines_to_del_to_del.append((ctx_keys_dl, save_line))
+
                 """
                 We changed how we display the neighbor interface command. Older
                 versions of frr would display the following: